This invention relates to a novel apparatus for sensing a predetermined liquid level, e.g., a low level, in a fluid reservoir. More particularly, this invention concerns a liquid level sensor which is insertable through the tube of a conventional dipstick in order to sense a predetermined level in a fluid reservoir, e.g., the oil level in a crankcase of an internal combustion engine.
In the past it has been common to determine the level in a fluid reservoir which is entirely enclosed within an engine component housing, e.g., the oil level in a crankcase of an internal combustion engine or the fluid level and automatic transmission fluid reservoir. The dipstick is inserted through a tube extending to the reservoir and subsequently removed, with the fluid, i.e., oil, adhering to the dipstick and indicating the level within the reservoir. Such a method of determining whether the level is low or high in the fluid reservoir has the disadvantage of requiring that the operator remove the dipstick to wipe the end of the dipstick clean, and then reinsert and subsequently remove it again to read the level of oil in the reservoir. Thus no remote indication of the oil level is possible, and in the case of an automobile engine, the automobile must be stopped and the hood opened in order to gain access to the engine. Thus there is no determining the existence of a predetermined level from inside the automobile.
The problems of the prior art enumerated in the foregoing are not intended to be exhaustive, but rather are among many which tend to impair the effectiveness of previously known methods and apparatus for detecting a predetermined level in a totally-enclosed fluid reservoir, e.g., in the crankcase of an internal combustion engine or the fluid reservoir of an automatic transmission. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that methods and apparatus for detecting a predetermined level in a fluid reservoir appearing in the prior art have not been altogether satisfactory, or at best overly expensive.